FLINT — A former Michigan health official testified Thursday that he started asking questions about bacteria in Flint's water supply a year before the state publicly acknowledged an outbreak of Legionnaires' disease.

Tim Becker, who was deputy director at the Department of Health and Human Services, acknowledged that the agency could have issued a public warning in January 2015. But it was 12 more months before the department and Gov. Rick Snyder said something publicly.

Becker was the first witness at a key court hearing involving his former boss, department director Nick Lyon, who is charged with involuntary manslaughter in the death of an 85-year-old man and misconduct in office.

A judge must decide whether there's enough evidence to send him to trial. Lyon's attorneys call the charges "baseless."

The attorney general's office says a timely announcement about a Legionnaires' outbreak in the Flint area in 2014-15 might have saved Robert Skidmore. He died of congestive heart failure, six months after he was treated for Legionnaires'.

Some experts have blamed the outbreak on Flint's use of the Flint River as a water source. At the same time, a failure to treat the water for corrosion caused a different disaster: Lead leached from old plumbing and contaminated the city's water system.

"I don't care whether you're 50 or 98, the fact is if someone had a role or responsibility in causing a death, justice demands, requires, that there is accountability," Attorney General Bill Schuette, whose office charged Lyon, told Crain's in June. "Nobody's expendable."

Schuette's legal team on Thursday needed to persuade the judge in the case, David Goggins, of probable cause, though some experts and state officials have disagreed on there being a direct link between the death and the Flint water crisis, The Detroit Newsreported.

Prosecutors would need to prove that link at trial.

"You are going to have to show that these increased, dangerous impurities in the water present a clear and immediate danger, and you have to show that these impurities in the water actually caused the Legionnaires' disease," Adam Candeub, a law professor at Michigan State University, told The News. "That's a very high, causal hurdle to get over because people get Legionnaires' disease for all sorts of reasons."

Nearly 100 Legionnaires' cases, including 12 deaths, were detected in 2014-15 while Flint was using the river. Legionnaires' is a type of pneumonia caused by bacteria, called legionella, that thrive in warm water and infect the lungs.

Skidmore's home wasn't on Flint water, but it's believed he got Legionnaires' while in a Flint hospital.

An infectious disease specialist hired by the state to investigate Legionnaires' after the outbreak became public in 2016 testified that Lyon seemed dismissive at times.

Marcus Zervos, M.D., quoted him as saying, "People are going to die of something."

Special prosecutor Todd Flood played a video of Lyon's testimony to a House-Senate committee in which he said he only learned about "major health issues" in Flint in July 2015. Flood revealed a January 2015 email in Lyon's account with "legionella" in the subject line.

Lyon is the highest-ranking official among 15 people charged in an investigation of how Flint's water system became poisoned after the city used the Flint River for 18 months, starting in 2014.